@isTest
private class DeleteOldDataScheduleTest {
    public static String CRON_EXP = '0 0 0 15 3 ? 2040';

    static testMethod void testMethod1() {
        ClockInOutHistory__c c1 = new ClockInOutHistory__c();
        ClockInOutHistory__c c2 = new ClockInOutHistory__c(ClockInTime__c = System.now());
        insert new ClockInOutHistory__c[] {c1, c2};

        System.Test.startTest();
        System.schedule('DeleteOldDataScheduleTest', CRON_EXP, new DeleteOldDataSchedule());
        System.Test.StopTest();

        List<ClockInOutHistory__c> clist = [select Id from ClockInOutHistory__c];
        System.assertEquals(1, clist.size());
    }
}